Photosynthesis and chemosynthesis - in what distinction?
Which of us does not remember definition “ photosynthesis “ from botany lessons at school? “ Process of formation of organic substance of carbon dioxide and water on light with the participation of photosynthetic pigments “. Knowing by heart this laconic definition very few people from us asked a question and what it hides for itself?
On - to a being, photosynthesis is a chemical reaction as a result of which six molecules CO2 connect to six molecules of water and one molecule of glucose - a construction brick of our organic substance is formed. The molecular oxygen which is formed during photosynthesis is only a by-product. However this most “ by-product “ is one of the main sources of atmospheric oxygen, so necessary for the higher organisms.
It would seem, everything is very simple: the cage of a photosynthesizing organism is some kind of “ flask “ for chemical reaction of two components. But in actual fact the mechanism of reaction is much more difficult. It appears, process consists of two reactions: “ light “ and “ dark “. The first is connected with splitting of a molecule of water on hydrogen and oxygen by means of energy of light. The sunlight is absorbed by a special light-absorbing pigment of a cage a chlorophyll (it is painted in green color). Further there is a transfer of energy to molecules ATP which release the received energy at the second stage of photosynthesis - “ dark “ reactions. “ Dark “ reaction is directly reaction between carbon dioxide and hydrogen with formation of glucose.
Plants, seaweed and some species of microorganisms can carry out photosynthesis. Thanks to their activity, there is possible an existence, for example, of animals whose food consists of organic substances. But whether photosynthesis is the only form of the transfer of carbon dioxide to organic substance? No. It appears, the nature provided also another, alternative, a way of formation of organic substances from CO2 - chemosynthesis .
Difference of chemosynthesis from photosynthesis is absence “ light “ reactions. As a power source, cages of hemosinteziruyushchy organisms use energy not of a sunlight, and energy of chemical reactions. What? Reactions of oxidation of hydrogen, carbon monoxide, restoration of sulfur, iron, ammonia, nitrite, antimony.
Of course, each hemosinteziruyushchy organism uses own chemical reaction as a power source. For example, hydrogen bacteria oxidize hydrogen, nitrifying bacteria transfer ammonia to a nitrate form etc. However all of them accumulate the energy which is released in the course of chemical reaction in the form of molecules ATP. Further process proceeds as reactions of a dark stage of photosynthesis.
Only some species of bacteria possess ability to chemosynthesis. The role them in the nature is enormous. They not “ make “ atmospheric oxygen, do not accumulate large amounts of organic substance. However chemical reactions which they use during the activity play a key role in biogeochemistry, providing, including, circulation of nitrogen, sulfur and other elements in the nature.